Austin90RS

So part of my 305 rebuild were ProForm 66927C 1.6 roller rockers arms and slightly bigger pushrods (+.100'' - 7.900) for the cam I got, and now I've gone thru 3 shattered rocker arms, (2 on #8 cyl. and 1 on#3) 2 of which broke when setting valve lash the day after i first started the motor with the new parts(about an solid hour of run time)...and today after waiting a week for a alternator to ship(hasn't been started in a week) I had the motor idling for about 10 minutes and hear a loud DING on the right valve cover and sure enough another broken rocker...could it be just cheap rockers? or maybe the factory springs are to stiff and the rockers can handle the stress?

PLEASE HELP!!!!!!!!

Orr89RocZ

iTrader: (20)

If its a roller cam those pushrods are way to long. Did you measure pushrod length before installing

If not that did check max lift? What cam? Could be coil binding the springs

Edwardgp

OMG never seen anything like this before. What ever is going on it is busting the heck out of those rocker arms.

Austin90RS

Thanks for reply, Its actually a flat tappet, I put a Jegs 200105 cam in,lifts around .460 in. and 480 ex.

Austin90RS

http://www.jegs.com/i/JEGS+Performan...00105/10002/-1 specs for cam

Orr89RocZ

iTrader: (20)

If you are positive nothing was binding up and pushrod length was fine and also not binding, and you were not coil binding the springs, then i would assume bad rockers and you should contact proform.

Quzyle

iTrader: (1)

Just a thought, you said that it has been rebuilt. Did you by chance use 350 heads on your 305? I have heard rumors of the valves contacting the block in this case. I could be totally wrong!

87zjeff

iTrader: (4)

what is the max lift the factory heads can handle? those specs listed are for 1.5 rockers. you have 1.6 plus longer pushrods. that will change the lift at the valve like having a bigger cam. i think Orr is right.

84ws6ta

I had this same issue when using these types of rocker arms. Mine were standard 1.5 ratio with a mild lift. Blew 2 out like above and found all but one in various stages of stress cracking. These rocker arms are cast and therefore more prone to cracking under high stress. The stress develops on the slot slamming back and forth on the rocker stud. I replaced mine with extruded aluminum roller rockers from Scorpion and haven't had an issue since.

Berlyn0963

iTrader: (4)

i use proform self aligned full roller 1.6's on my 350 crate and never looked back.